Method of making molds



Patented Jan. 3, 1933 UNITED STATES PATENT OFFICE EDWARD TOHAN, OFCHICAGO, ILLINOIS, ASSIGNOB TO B. TOMAN & COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS I METHOD OF MAKING HOLDS RDrawing.

' This invention relates to a method of forming molds, particularly suchas are used in the making of the castings of non-ferrous metals.

In the making of molds of such materials as calcium sulphate, or plasterof Paris, which depend upon water of crystallization for their set, ithas been the custom to 1111K the sulphate and water together in aseparate puddling operation to form a plastic material. The plastic isthen forced into afiask and about a pattern or form. A wire brush 01'similar instrument is used in order to pack the material about the form,and also to penetrate any air bubbles which might form in the material.The purpose is to secure a uniform and dense deposit of the plasticabout the form.

Such. a method has the disadvantage that the plaster of Paris reactswith the water so rapidly that the water is largely used up and thematerial partially set before it can be properly packed into the mold.Therefore it is extremely difficult, even with utmost care, to secureuniformity by puddling the plastic separately and then applying it to amold with the use of a brush.

It is an object of this invention to provide a method of making moldswhich does not have the above named disadvantages.

It is a further object of this invention to produce a mold by a methodin which the hydrated form of the material is formed directly in theflask containing the pattern and e a rapid set is obtained.

It is a still further object of this invention to produce a mold by amethod which insures that the maximum amount of water will be quicklytaken up by the sulphate and that the plastic mass will be uniformthroughout.

These and further objects of th s inventionwill be apparent from thefollowing description of a preferred form and from the appended claims.

In carrying out this invention, a container.

or flask, is provided, on the bottom of which the pattern or object isformed. The container preferably has easily assembled sides and endwalls or barriers and a removable COVGI'.

Serial No. 549,097.

terial. A predetermine amount of water is then added.

The sidewalls or barriers of the container should be so proportioned tothe pattern formed on the bottom that the water will be sufficientlyhigh to permit a space for the hy- 1 drating action. A plate or cover isplaced over the top of the barriers and the container and contents issubjected to a rapid shaking.

The container is moved rapidly back and forth and up and down, and infact in every direction at a high rate of speed, to distribute the waterthrough the material. Such an action insures that the water will bedistributed through the material in an even manner. The water is thuscaused to travel at a high rate of speed through the plastic formingmaterial and then to impact against the pattern and cover plate. Thesurface tension is thus overcome, permitting the compacting of the thelatter begins to hydrate and gradually set. The motion insures thatthere will be no air pockets formed, and also that the plastic materialthus formed will be even throughout, and will closely follow the patternor object.

The amount of water to be used is calculated from the followingequation:

The molar proportion of plaster of Paris to water is 1 to 3, or threeparts by weight of water to sixteen parts by weight of plaster of Paris.The amount of water actually used is usually from 15 to 25 per cent inexcess of the calculated amount.

It will be seen by this method, that the water comes into intimatecontact with the minutest particles of the dried material, whereby veryrapid and very thorough hy- 5 dration is achieved. The mec anicalmotlons of the particles and the water insure that not only will'therebe no air pockets but also the hydrated or lastic material thus formedwill shape itsel uniformly about the pattern.

Many changes may be made in the details and arrangements in carrying outthe process and I do not wish to be limited otherwise than is necessary,by the prior art and the sco e of the appended claims.

I am aware that numerous details of the process may be varied through awide range without departing from the principles of this invention, andI, therefore, do not purpose limiting the patent granted hereonotherwise than necessitated by the prior art.

I claim as my invention:

1. .The method of forming a mold, which comprises, adding a'plasterforming powder 'to a container having a pattern formed on one wallthereof, the amountofthe owder being suflicient to thoroughly cover t eattern, adding a predetermined amount 01 water, closing the container,vigorously a 'tating the container and contents to cause t e contents toimpact against the sides and top of the container .to thereby cause thepowder to thoroughly absorb the water and allowing the plastic mixtureto set.

2. The method of forming a mold, which comprises adding powdered plasterof Paris to a flask having a pattern formed on one wall thereof, theamount of powder being suflicient to thoroughl cover the pattern,

adding slightly more t an enough water to change the powdered plaster ofParis to the hydrated form, closing the flask, vigorously agitating theflask and contentssuccessively vertically and horizontally to cause thecontents to impact against the side and top of the flask to therebycause the powder to thoroughly absorb the water and allowing thehydrated form to set.

3. The method of forming a mold which comprises adding powdered plasterof Paris to a flask having a pattern formed on one wall thereof, insuflicient quantity to cover the pattern, adding slightly more thanenough water to change the powdered plaster of Paris to the hydratedform, closing the flask and vigorously agitating the flask and contentsto impact the contents against the pattern and the side and top of theflask to cause the powder to thoroughly absorb the water,

(so and allowing the hydrated form to set.

In testimony whereof I have hereunto subscribed my name at Chicago,Cook. county,

Illinois.

EDWARD TOMAN.

